The present invention relates to a thermostatic valve device, particularly for a coolant circulating system of an internal-combustion engine, having a thermostatic working element which has a housing containing an expansion material and a working piston which can be moved out of the housing. The working piston is supported on an abutment in such a manner that, when the working piston moves out, the housing, which is connected with a valve disk, moves against the action of a restoring spring and lifts the valve disk off a valve seat. The thermostatic valve device has a pilot valve.
Thermostatic valve devices are used in large quantities particularly for controlling the coolant circulating systems of internal-combustion engines in motor vehicles. A problem exists in the case of cold starts. In other words, when the internal-combustion engine is started and the coolant is heated to the operating temperature. When the opening temperature is reached, the valve will open up immediately with a relative large valve cross-section so that, as a rule, there is a relatively high overshooting. A certain improvement has been achieved when the characteristic operating curve in this area is influenced by a special design of the valve seat, specifically by the so-called "pilot valve" seat.
In order to improve the characteristic operating curve in this area, it is also known to integrate an additional pilot valve into the thermostatic valve device. It is also known to arrange in the valve disk of the thermostatic valve device a small additional thermostatic valve as the pilot valve with an additional thermostatic working element. This pilot valve opens up before the opening temperature of the main thermostatic valve device is reached.
In German Patent Document DE-C 31 01 248, a valve disk is shown held on the housing of the thermostatic working element in a "floating" manner. The valve disk is arranged between a disk-type take-along device mounted on the housing and a spring such that the first movement of the housing, when the working piston is moved out, bridges a sort of "idle path." In other words, the valve disk is not yet taken along. In this case, a flow path is exposed between the housing of the thermostatic working element by which the pilot valve effect is obtained. The valve disk will be not be taken along by the housing of the thermostatic working element before the idle path is bridged so that the take-along device comes to rest against the valve disk and takes it along.
An object of the invention is to provide a thermostatic valve device of the initially mentioned type which is distinguished by a simple construction and by a reliable operation.
This and other objects are achieved by the present invention which provides a thermostatic valve device for a coolant circulating system of an internal-combustion engine having a thermostatic working element which has a housing containing an expansion material and a working piston which is movable out of the housing in a moving-out direction. A valve disk and a valve seat forms a valve. The valve disk is connected to the housing. A restoring spring is coupled to the housing. An abutment supports the working piston such that, when the working piston moves out, the housing moves against the action of the restoring spring to lift the valve disk off the valve seat. The abutment is a thrust bearing. An idle path is between the abutment and the working piston. The idle path is bridged by a first part of the moving-out movement. A bypass connection bypasses the valve. A closing member is mounted on the working piston and closes and opens the bypass connection. The bypass connection and the closing member form a pilot valve which opens during the moving-out of the working piston for bridging the idle path. A closing spring is coupled to the closing member and loads the closing member against the moving-out direction of the working piston.
By means of the construction according to the invention, a pilot valve is provided which not only has a pilot effect improving the characteristic operating curve but, in addition, acts as a pressure relief valve. In particular, when the thermostatic valve device is used as a throttle control device, there is the risk that, when the coolant is cold before the thermostatic valve device responds, such a high excess pressure is built up there damages may occur. In this case, the pilot valve is also used which, because of its construction and arrangement, opens up not only when its opening temperature is reached but also when an excess pressure occurs which can be adjusted by means of its closing spring.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.